What is the easiest way to calculate TAM?

Bottom-up: number of potential customers × annual revenue per customer. It forces you to define the buyer and the price. Use top-down analyst figures as a sanity check.

Should I show both top-down and bottom-up?

Yes when you can. If they diverge by more than ~3×, explain why — different category definitions are usually the culprit. Investors respect the reconciliation.

Can AI calculate TAM for me?

AI can draft a sourced TAM/SAM/SOM stack quickly. You still own the assumptions. Tamfinder generates a filing with methodology and citations you can stress-test before a pitch.

Playbook // Calculation

How to calculate TAM

A practical playbook for Total Addressable Market — top-down, bottom-up, and how to turn the result into SAM and SOM without inventing percentages.

Step 1 — Define the product category

Write one sentence: who buys, what they buy, and what substitutes exist. "AI scheduling for dental clinics" is a category. "Healthcare software" is not. Bad category definitions are the #1 reason TAM numbers get laughed out of partner meetings.

Step 2 — Bottom-up TAM

TAM = (# of potential customers) × (annual spend per customer)

Count customers from census, registries, CRM lists, or scraped directories.
Price from comps, surveys, or your own willingness-to-pay work.
State assumptions inline (e.g. "180k US dental practices × $2.4k ACV").

Step 3 — Top-down TAM

Find a credible category report. Narrow with explicit filters (geo, segment, product type) until it matches your definition. Cite the source, year, and the narrowing steps. If you cannot cite it, do not use it.

Step 4 — Derive SAM and SOM

Apply reachability filters for SAM, then build a go-to-market model for SOM. Never set SOM as a naked percentage of TAM. Full context: TAM, SAM & SOM explained.

Step 5 — Show the work

Investors buy the methodology, not the headline number. Every Tamfinder filing includes methodology cards and sources for this reason — browse recent market filings for examples, or generate yours below.

FAQ

What is the easiest way to calculate TAM?: Bottom-up: number of potential customers × annual revenue per customer. It forces you to define the buyer and the price. Use top-down analyst figures as a sanity check.
Should I show both top-down and bottom-up?: Yes when you can. If they diverge by more than ~3×, explain why — different category definitions are usually the culprit. Investors respect the reconciliation.
Can AI calculate TAM for me?: AI can draft a sourced TAM/SAM/SOM stack quickly. You still own the assumptions. Tamfinder generates a filing with methodology and citations you can stress-test before a pitch.

Size your idea free

Paste a one-sentence startup idea. Get sourced TAM, SAM, SOM and a fundability verdict.